Allowance for Loan and Lease Losses - Credit Risk Profiles (Details)	9 Months Ended
	Sep. 30, 2019 USD ($) factor	Dec. 31, 2018 USD ($)
Credit quality
Percentage of loans sold with no recourse not subject to grading	100.00%
Number of risk factors in internal loan rating system | factor	8
Loans and leases	$ 12,843,396,000	$ 13,076,191,000
Loss
Credit quality
Loans and leases	0	0
Commercial Lending
Credit quality
Loans and leases	6,618,317,000	6,974,069,000
Commercial Lending | Pass
Credit quality
Loans and leases	6,288,589,000	6,718,416,000
Commercial Lending | Special mention
Credit quality
Loans and leases	245,821,000	149,733,000
Commercial Lending | Substandard
Credit quality
Loans and leases	83,907,000	105,728,000
Commercial Lending | Doubtful
Credit quality
Loans and leases		192,000
Commercial and Industrial
Credit quality
Loans and leases	2,654,077,000	3,208,760,000
Commercial and Industrial | Pass
Credit quality
Loans and leases	2,498,746,000	3,069,546,000
Commercial and Industrial | Special mention
Credit quality
Loans and leases	119,553,000	57,012,000
Commercial and Industrial | Substandard
Credit quality
Loans and leases	35,778,000	82,010,000
Commercial and Industrial | Doubtful
Credit quality
Loans and leases		192,000
Commercial real estate
Credit quality
Loans and leases	3,309,389,000	2,990,783,000
Commercial real estate | Pass
Credit quality
Loans and leases	3,139,428,000	2,876,907,000
Commercial real estate | Special mention
Credit quality
Loans and leases	125,082,000	91,298,000
Commercial real estate | Substandard
Credit quality
Loans and leases	44,879,000	22,578,000
Construction
Credit quality
Loans and leases	486,977,000	626,757,000
Construction | Pass
Credit quality
Loans and leases	483,535,000	625,607,000
Construction | Special mention
Credit quality
Loans and leases	308,000	200,000
Construction | Substandard
Credit quality
Loans and leases	3,134,000	950,000
Lease financing
Credit quality
Loans and leases	167,874,000	147,769,000
Lease financing | Pass
Credit quality
Loans and leases	166,880,000	146,356,000
Lease financing | Special mention
Credit quality
Loans and leases	878,000	1,223,000
Lease financing | Substandard
Credit quality
Loans and leases	116,000	190,000
Residential and consumer
Credit quality
Loans and leases	6,225,079,000	6,102,122,000
Residential and consumer | Performing
Credit quality
Loans and leases	6,177,093,000	6,040,469,000
Residential and consumer | Non-performing and delinquent
Credit quality
Loans and leases	47,986,000	61,653,000
Residential Mortgage.
Credit quality
Loans and leases	3,671,424,000	3,527,101,000
Residential Mortgage. | Performing
Credit quality
Loans and leases	3,663,274,000	3,519,172,000
Residential Mortgage. | Non-performing and delinquent
Credit quality
Loans and leases	8,150,000	7,929,000
Home equity line
Credit quality
Loans and leases	916,106,000	912,517,000
Home equity line | Performing
Credit quality
Loans and leases	910,032,000	903,284,000
Home equity line | Non-performing and delinquent
Credit quality
Loans and leases	6,074,000	9,233,000
Consumer
Credit quality
Loans and leases	1,637,549,000	1,662,504,000
Consumer loans | Consumer
Credit quality
Loans and leases	236,881,000	239,906,000
Consumer loans | Consumer | Performing
Credit quality
Loans and leases	230,849,000	234,458,000
Consumer loans | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	6,032,000	5,448,000
Consumer - Auto | Consumer
Credit quality
Loans and leases	1,051,366,000	1,078,132,000
Consumer - Auto | Consumer | Performing
Credit quality
Loans and leases	1,029,124,000	1,044,393,000
Consumer - Auto | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	22,242,000	33,739,000
Credit Cards | Consumer
Credit quality
Loans and leases	349,302,000	344,466,000
Credit Cards | Consumer | Performing
Credit quality
Loans and leases	343,814,000	339,162,000
Credit Cards | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	$ 5,488,000	$ 5,304,000